By Joe Marin

The last time PIA/GATF conducted a survey on the reasons for printers’ rework, unacceptable color was number one. Couple this with the fact that a lack of knowledge about color and fuzzy customer/printer communications is the source for many of those problems, and a key improvement opportunity is staring you in the face.

While it is not always clear what can be done to address the vague statement of “poor communications,” in this instance, there is something you can do about it. Education about some of the most common color issues will help streamline the color reproduction process and avoid the agonizing need for rework.

Here are eight items that it would be wise to be aware of:

1. Consistency for viewing color. One important method for assuring color consistency is to agree on standard lighting conditions for viewing color proofs and press sheets. In order to reduce variables in the color communication and reproduction process, the graphic arts industry has established standard color viewing conditions called a standard color viewing booth.

There are two things that make a color-viewing booth special: the lighting (referred to as 5,000 K) and a neutral gray surround (referred to as Munsell N8 gray).

Viewing color in a viewing booth is important because the lighting conditions and the surrounding environment in which we view color will influence color perception. If there is no viewing booth available, the next best condition (closest to 5,000 K) is indirect sunlight.

2. The effect of lighting. Color when viewed under different lighting conditions will look different. Another issue with lighting and viewing color is metamerism, which occurs when two color samples appear to match under a particular light source, and then do not match under a different light source.

This is a strong argument for consistent lighting for color viewing. 5,000 K is used because it contains an even mix of red, green and blue wavelengths. The lighting in viewing booths is neutral for proper and consistent color viewing when approving a job.

3. The effect of the surround. How does the surrounding environment in which we view a proof or a press sheet influence the color? Adjacent colors, that is, colors that are adjacent to the proof or press sheet being viewed, can influence color perception.

This phenomenon is called the “adjacency effect” and illustrates why it is important to use a neutral surround when viewing a proof or a press sheet. Munsell N8 gray is used for the surround color to eliminate the influence of the surround when viewing color.

4. It’s all in the paper. Subtractive color refers to using cyan, magenta, yellow and black inks on a white surround (usually paper) to reproduce full color. One component of the color reproduction process has the greatest influence on how good the color will look when printed on press: the paper.

The same ink color will produce very different results when printed on various paper types. The whiter the paper is, the greater the color gamut that can be reproduced on press. As paper becomes less white (and less expensive), the color gamut that can be reproduced on press becomes smaller.

5. Spot color considerations. A spot color is a term given to a special ink (other than cyan, magenta, yellow and black) that is printed on its own unit of the printing press. There are many reasons why spot colors are used on a printed job. For example, when brand identification is important (such as Coca-Cola red or Ford blue), it is important the corporate identity color is reproduced perfectly.

Another reason might be the use of metallic inks. Metallic inks contain flakes of metal powder and produce printed content with a shiny, metallic luster. Finally, spot colors are often used when the design calls for a color beyond the gamut of what CMYK (process color) inks can reproduce.

6. Converting color to CMYK. When images are converted from RGB into CMYK, the halftone dots for the black ink are typically generated in one of two ways: using undercolor removal (UCR) or gray component replacement (GCR). This choice determines how much black is introduced into the image, as well as how much cyan, magenta and yellow ink will be printed.

UCR reduces the amount of cyan, magenta and yellow and increases the amount of black in areas where black is already present. UCR primarily affects the shadow areas of the image and does not affect color areas. Images are more susceptible to color shift throughout the pressrun when images are separated with UCR.

GCR also reduces the amount of cyan, magenta and yellow and increases black. However, GCR is more aggressive; it occurs when only cyan, magenta and yellow are present. Images separated with GCR tend to print more consistently throughout the pressrun, but can hinder the press operator’s ability to make color adjustments on press.

7. Terminology is everything. Describing color is difficult because it is a sensation; it’s as difficult as trying to describe all of our other sensations: how something smells, tastes or sounds, for example. Often, vague terms such as “flat,” “muddy,” “too warm,” “too cold” or “needs more snap” are used to describe color.

For example, what if an image is too warm? Does “too warm” mean too red, too yellow or too magenta? Does “too cold” mean too blue, too green or too cyan? “Flat” typically refers to lacking in contrast, while “muddy” typically means too dark. Using imprecise terminology will result in additional proofing cycles, delaying the production process. The bottom line: use correct terms when communicating color – it can save time and money.

8. Printing is not an “exact match” process. What is a reproduction? A reproduction is not an exact match; a reproduction is a likeness, or close facsimile. Printing is not an exact match process. This is because there are many color reproduction systems within the color reproduction process.

Photography is one example of a color reproduction system; proofing and the pressrun are others. As we compare what the eye can see, to what photography can capture, to what the press can reproduce, the color gamut (or number of reproducible colors) is diminished.

Please post a Comment to this Tip – and let others benefit from your wisdom. Thanks.

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Joe Marin, senior analyst of digital technologies, specializes in up-and-coming digital technologies in print production workflow and leads several Printing Industries of America (PIA) training programs, including Orientation to the Graphic Arts. He also contributes to other training programs and conducts seminars at leading trade shows. Joe is the author of “Process Controls Primer, Digital Prepress Primer,” and co-author of “The PDF Print Production Guide.” Joe can be reached by phone: 412-259-1731 or e-mail: jmarin@piagatf.org.

This article is reprinted with permission from the 2008 GATFWorld. Copyright 2008 by the Printing Industries of America/Graphic Arts Technical Foundation. All rights reserved.